For those of us who are doing B2B cruises this is what I found out about how it works between cruises from another thread. This is from the Wonder but I'm sure something similar will be happening on the Dream.
Not quite cool enough these days, sorry. I believe they used to let you stay onboard, but not now.
The process is simple, and actually good fun.
You get your info the night before. If you are changing rooms you pack up ad leave everything in your room and it all gets moved for you. You do need to take your old room key and all your new cruise documents as normal, plus stuff you will need for a couple of hours out of your room.
I popped a couple of loads in the washer, putting a sticky note on the washer to say we were still onboard.
They give you a time to meet somewhere. I think it was about 9.30am in Sessions. Once everyone getting off the ship has done so, you are all escorted off, then back into the terminal. The terminal building is all empty, and great for photographs. Very quickly someone comes to check you in, and when you are all done, they let you back onboard. I think we were onboard for not long after 10am. It is all a very painless procedure.
If you have kept your same room, you can go back there, but don't want you going under the tape blocking the room corridors once all the new cruisers are onboard, or they want to do that too!!!! But it means you can go get all your laundry finished. If you are changing rooms then the normal 1.30pm rule will apply, unless you know the room steward and your room is finished early.
You can wander the ship and get great photos. You base yourself at Cove Cafe, and they have a few pastries there. The drinks station should be open. Otherwise there is nothing until the buffets open at 12md.
We had a starboard room so it was great watching all the ship side activity.
I loved our changeover day and didn't think it a wasted day.